2,2,2-trifluoroethanol (CF.sub.3 CH.sub.2 OH) is known to be useful as an intermediate in the formation of the anesthetic CF.sub.3 CH.sub.2 OCHF.sub.2. CF.sub.3 CH.sub.2 OH is also known to be useful as a working fluid in a Rankine cycle, as disclosed in U.S. Pat. No. 3,722,211. CF.sub.3 CH.sub.2 OH is also useful as a sovlent in nylon processing. Other fluorinated alcohols are also useful as intermediates.
Commerical processes for producing CF.sub.3 CH.sub.2 OH usually proceed by oxidation of a perhalogenated ethane, such as CF.sub.3 CCl.sub.3 to CF.sub.3 COCl followed by esterification with CF.sub.3 CH.sub.2 OH to form CF.sub.3 CO.sub.2 CH.sub.2 CF.sub.3 (2,2,2-trifluoroethyl trifluoroacetate) which is then hydrogenated over a catalyst to form 2 moles of CF.sub.3 CH.sub.2 OH for each mole of ester. One mole of CF.sub.3 CH.sub.2 OH is recycled to esterify more acid.
This invention is concerned with an improvement in the catalyst performance for the final step of this process, namely the hydrogenation of CF.sub.3 CO.sub.2 CH.sub.2 CF.sub.3, preferably at atmospheric pressure. It is also concerned with improved methods of hydrogenation of fluorinated esters generally.
It has previously been reported in U.S. Pat. No. 3,356,747 that a barium promoted copper chromite catalyst could hydrogenate such esters and especially CF.sub.3 CO.sub.2 CH.sub.2 CF.sub.3. Typically, the catalyst contains a mixture of 44% CuO, 47% CrO.sub.3 and 9% BaO in which the molar ratio of CuO/copper chromite is 0.8/1.0 and BaO is the promoter. Such catalysts, although generally successful, occasionally exhibit the disadvantage of erratic performance and a catalytic life shorter than desired. Thus, prior art processes may require a larger amount of catalyst being used per quantity of fluorinated alcohol and a more frequent replacement of catalyst in the reaction chamber than may be preferred.
Catalysts containing both CuO and Na.sub.2 SiO.sub.3 are known and are generally used as hydrogenation catalysts for converting aldehydes to alcohols and removing trace amounts of oxygen, carbon monoxide and hydrogen from gas streams. Such a product containing CuO and Na.sub.2 SiO.sub.3 in varying proportions is manufactured and sold by the Harshaw Chemical Company under the tradename Cu 1710. Use of such a catalyst for ester reductions has not been recommended, based in part upon the work of Adkins et al., J. Am. Chem. Soc., Vol. 72, 2626 (1950), who reported that cupric oxide alone is ineffective in the hydrogenation of esters and that the activity of copper chromite catalysts is dependent upon the ratio of cupric oxide to copper chromite. Adkins postulates that, in the absence of copper chromite, CuO is reduced to copper.
It has thus been suprisingly found according to the present invention, that cupric oxide, in the absence of chromite, is an effective hydrogenation catalyst for certain highly fluorinated esters, and particularly, the hydrogenation of CF.sub.3 CO.sub.2 CH.sub.2 CF.sub.3.